docs: def qxq(q1, q2):
      """
      Multiply two quaternions.
  
      http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/qxq_c.html
  
      :param q1: First SPICE quaternion.
      :type q1: 4-Element Array of floats
      :param q2: Second SPICE quaternion.
      :type q2: 4-Element Array of floats
      :return: Product of q1 and q2.
      :rtype: 4-Element Array of floats
      """
      q1 = stypes.toDoubleVector(q1)
      q2 = stypes.toDoubleVector(q2)
      vout = stypes.emptyDoubleVector(4)
      libspice.qxq_c(q1, q2, vout)
      return stypes.cVectorToPython(vout)